Non Destructive Evaluation and Structural Health Monitoring : A Review

Structural health monitoring has great potential for enhancing the functionality, serviceability and increased life span of structures. Structural health monitoring is defined as “continuous, autonomous, real time, in-service monitoring of the physical condition of a structure by means of embedded or attached sensors with minimum manual intervention". This need which arises from the fact that intensive usage combined with long endurance causes gradual but unnoticed deterioration in structures, often leading to unexpected disasters. Recently smart piezoelectric-ceramic lead material is emerged as high frequency impedance transducers for non-destructive evaluation. In this role, the PZT patches act as collocated actuators and sensors and employ ultrasonic vibrations gives a characteristic admittance ‘signature’ of the structure. The admittance signature has vital information about the nature of the structure, and it can be analysed to predict the onset of structural damages. PZT patches exhibit excellent performance as far as damage sensitivity. Their sensitivity is high enough to capture any structural damage at the incipient stage. There are different Non-Destructive techniques like acoustic emission, ultrasonic, acousto-ultrasonic, guided ultrasonic waves or Lamb waves. The Lamb wavebased active SHM method uses piezoelectric (PZT) sensors to transmit and receive wave. Thus, Lamb waves generated by PZT sensors and time-frequency analysis techniques could be used effectively for damage detection. This study has given a complete idea of the working and the basic requirements of SHM system.